单选题 He has just arrived, but he talks as if he ＿＿＿＿＿＿＿＿＿ all about what has happened. 的答案

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题目内容：
He has just arrived, but he talks as if he ＿＿＿＿＿＿＿＿＿ all about what has happened.
题目选项